Exhaust valve actuation system for diesel particulate filter regeneration

ABSTRACT

An exhaust valve actuation system ( 30 ) for initiating a regeneration event at a diesel particulate filter ( 24 ) includes an engine control module ( 42 ) associated with an engine ( 14 ). A plurality of exhaust valves ( 32 ) correspond to a plurality of engine cylinders (C 1 -C 6 ). When either a predetermined amount of back pressure or a predetermined temperature, or both, are communicated to the engine control module ( 42 ), the engine control module actuates at least one exhaust valve ( 32 ) to open. Gas or gas-fuel mixture is compressed and heated inside of the cylinder (C 1 ) corresponding to the opened exhaust valve ( 32 ). At least one exhaust valve ( 32 ) is not opened by the engine control module ( 42 ), which permits combustion inside the corresponding cylinder (C 2 ).

BACKGROUND

Embodiments described herein relate to a system and method for heatingexhaust gas. More specifically, embodiments described herein relate to asystem and method for heating exhaust gas to create a regeneration eventat a diesel particulate filter.

Exhaust gas aftertreatment systems in diesel vehicles are locateddownstream of the engine for treating exhaust gases emitted from theengine. The aftertreatment systems typically include a diesel oxidationcatalyst (DOC), and a diesel particulate filter (DPF). Particulatematter from the exhaust gas accumulates on the diesel particulatefilter, and if left unchecked, can create a back pressure in theaftertreatment system and the diesel engine. Without a regenerationevent, the DPF can become plugged with soot and the engine may notoperate properly.

The regeneration event is the periodic oxidation of the collectedparticulate matter in the aftertreatment system during routine dieselengine operation. When the diesel particulate filter of the exhaustsystem experiences a build-up of particulate matter, the particulatematter is oxidized to “regenerate” the filter. Regeneration is typicallyinitiated by increasing engine load and activating a post-injection ofdiesel fuel into the exhaust stream. The combination of the increasedengine load and the post-injection provides sufficient heat to oxidizethe trapped particulate matter within the diesel particulate filter.

During idling or part load operation conditions, fuel injected into thecombustion cycle is not enough to maintain exhaust gas temperaturesufficient to start the DPF regeneration cycle. As such, the loading ofthe engine must be increased to provide a sufficiently heated exhaustgas to initiate the regeneration downstream at the diesel particulatefilter. However many vehicles operate on a “stop and drive” or frequentidling basis, and the resulting exhaust gas may not have a sufficientlyhigh temperature to initiate the regeneration.

SUMMARY

An exhaust valve actuation system for initiating a regeneration event ata diesel particulate filter includes an engine control module associatedwith an engine. A plurality of exhaust valves correspond to a pluralityof engine cylinders. When either a predetermined amount of back pressureor a predetermined temperature, or both, are communicated to the enginecontrol module, the engine control module actuates at least one exhaustvalve to open. Gas is compressed and heated inside of the cylindercorresponding to the opened exhaust valve. At least one exhaust valve isnot opened by the engine control module, which permits combustion insidethe corresponding cylinder.

A method of regenerating an exhaust aftertreatment system of an engineincludes the steps of providing a fluid passageway from the engine to adiesel particulate filter. The method also includes the steps of sensingand communicating a back pressure of the aftertreatment system or atemperature of the aftertreatment system, or both, to an engine controlmodule. The engine control module compares the back pressure or thetemperature, or both, to a predetermined back pressure or temperature,or both. On the basis of the comparison, the engine control moduleactuates at least one exhaust valve of a cylinder, and the exhaust valveis opened to compress gas inside of the cylinder. The heated compressedgas from the cylinder is fluidly communicated to the diesel particulatefilter. Not all of the exhaust valves are opened by the engine controlmodule so that combustion can continue to occur at the remainingcylinders. The heated exhaust gas from the remaining cylinders is alsofluidly communicated to the diesel particulate filter.

An exhaust valve actuation system for initiating a regeneration event ata diesel particulate filter includes an engine control module associatedwith an engine. The system also includes either a temperature sensor forsensing the temperature at the aftertreatment system, or a back pressuresensor for sensing the pressure at the aftertreatment system, or both.The temperature or the back pressure, or both, are communicated to theengine control module. A plurality of exhaust valves correspond to aplurality of cylinders in the engine. A high pressure oil manifold isassociated with the engine and has a shut-off valve that selectivelyprevents oil from an injector oil gallery from flowing to an exhaustvalve gallery. When either a predetermined amount of back pressure or apredetermined temperature, or both, are communicated to the enginecontrol module, the engine control module deactivates the shut-offvalve. Deactivation of the shut-off valve permits oil from the injectoroil gallery to flow to the exhaust valve gallery to open an exhaustvalve. At least one of the exhaust valves is not opened by the enginecontrol module to permit combustion inside the corresponding cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an engine having an exhaust aftertreatmentsystem with a diesel particulate filter located downstream of theengine.

FIG. 2 is a schematic of an exhaust valve actuation system for providingheated gases from the engine.

FIG. 3A is a section view of a high pressure oil manifold of the exhaustvalve actuation system when the system is not actuated.

FIG. 3B is a transverse section view of the high pressure oil manifoldof the exhaust valve actuation system when the system is not actuated.

FIG. 4A is a section view of the high pressure oil manifold of theexhaust valve actuation system when the system is actuated.

FIG. 4B is a transverse section view of the high pressure oil manifoldof the exhaust valve actuation system when the system is actuated.

DETAILED DESCRIPTION

Referring to FIG. 1, an exhaust gas aftertreatment system for a vehicleis indicated generally at 10, and has an exhaust pipe assembly 12extending from an engine 14 to an outlet 16, such as the outlet to anambient 18. The exhaust pipe assembly 12 forms a fluid passageway 20 forthe flow of exhaust gas F from the engine 14 to the ambient 18.

A first portion 22 of the exhaust pipe assembly 12 extends from theengine 14 to a diesel particulate filter (DPF) 24. The DPF 24 is afilter constructed from a very high temperature resistant material. TheDPF 24 catches and holds particulate matter entrained within the exhaustgases discharged into the exhaust aftertreatment system 10. The DPF 24is periodically regenerated to limit increases in exhaust aftertreatmentsystem 10 back pressure and to maintain engine 14 efficiency. A dieseloxidation catalyst (DOC) 26 may be located upstream of the DPF 24. Asecond portion 28 of the exhaust pipe 12 assembly extends from the DPF24 to the outlet 16. Other components may be disposed on the on theaftertreatment system 10.

Referring now to FIGS. 1-4B, an exhaust valve actuation system 30deactivates at least one cylinder C1 of the engine 14 from fuelinjection and combustion. The cylinder C1 is deactivated by opening anexhaust valve 32 corresponding to the deactivated cylinder, and usingcompressive forces to heat up the gas in the deactivated cylinder.

In the deactivated cylinder C1, a cylinder piston 34 compresses the airreceived by an air intake 36, which increases the temperature of theair. The heated air is released or bled from the cylinder C1 through thepartially opened exhaust valve 32 to an exhaust manifold 38 and on tothe DPF 24. The high pressure formed by compression in the cylinder C1is also a braking force that tends to resist the rotation of thecrankshaft (not shown) of the engine 14.

While the engine 14 of FIG. 1 has six cylinders C1-C6, it is possiblethat the exhaust valve actuation system 30 can be used on any enginewith at least two cylinders. Further, while the exhaust valve actuationsystem 30 deactivates at least one cylinder C1, the system maydeactivate an equal number of cylinders as the number of activatedcylinders, or alternately, an unequal number of cylinders. The exhaustvalve actuation system 30 described below opens the exhaust valves 32 ona plurality of the cylinders C1, C3, C5 in the engine 14.

At least one cylinder C2 is not deactivated by the exhaust valveactuation system 30. The remaining cylinders C2, C4, C6 that remainactivated continue to receive injected fuel at a fuel injector 40 andcombust the fuel to maintain the engine speed. To compensate for thedeactivated cylinders C1, C3, C5 that are not combusting fuel, and toovercome the resistance of the deactivated cylinders on the crankshaftof the engine 14, the activated cylinders C2, C4, C6 may receive anincreased amount of fuel at the fuel injector 40. The resulting exhaustgas from the activated cylinders C2, C4, C6 has an increasedtemperature.

The combination of the heated, compressed gas from the deactivatedcylinders C1, C3, C5, and the heated exhaust gas from the activatedcylinders C2, C4, C6, provides sufficient heat to the exhaust gas toinitiate regeneration at the DPF 24. With the exhaust valve actuationsystem 30, the engine 14 provides the heated, compressed gas from thedeactivated cylinders C1, C3, C5, and the heated exhaust gas from theactivated cylinders C2, C4, C6 while the engine 14 operates at a lowidling and low engine load condition.

The exhaust valve actuation system 30 includes an engine control module(ECM) 42 that controls an exhaust shut-off valve 44 mounted on a highpressure manifold 46. A brake control pressure sensor 48 and aninjection pressure sensor 50 may be disposed on the high pressuremanifold 38 to monitor and communicate the oil pressure in an exhaustvalve gallery 52, and the oil pressure in an injector oil gallery 54 ofthe high pressure manifold, respectively, to the ECM 42.

An exhaust back pressure sensor 56 monitors and communicates the backpressure in the aftertreatment system 10, such as at the exhaustmanifold 38 or the DPF 24, and communicates the back pressure to the ECM42. It is possible that the back pressure can be a change in pressurebetween two locations on the aftertreatment system 10, such as upstreamand downstream of the DPF 24.

A temperature sensor 58 senses the temperature at the DPF 24, theexhaust manifold 38, or anywhere between the cylinders C1-C6 and theDPF, and communicates the temperature to the ECM 42. It is possible thatthe temperature can be a change in temperature between two locations onthe aftertreatment system 10, such as upstream and downstream of the DPF24.

The ECM 42 has predetermined back pressure values, exhaust valve gallerypressure values, injector oil gallery pressure values, and temperaturevalues that are compared with the values communicated to the ECM by thesensors 48, 50, 56, 58. Below the predetermined temperature value ofaftertreatment system 10 at the sensor 58, or above the predeterminedpressure value of back pressure in the aftertreatment system 10 at thesensor 56, the DPF 24 may be clogged with soot or other particulatematter, and the exhaust valve actuation system 30 may be actuated.

Referring to FIGS. 2 and 3A-3B, during normal operation of the engine14, oil in the high pressure manifold 46 flows to the fuel injector oilgallery 54, but the exhaust shut-off valve 44 selectively prevents theoil from entering the exhaust valve gallery 52. During normal operation,all cylinders C1-C6 receive fuel from the fuel injector 40 and areactuated for combustion.

When a predetermined amount of exhaust back pressure is monitored by theexhaust back pressure sensor 56, or when a predetermined temperature ismonitored by the temperature sensor 58, the values are communicated tothe ECM 42 and the ECM 42 commands the actuation of the exhaust valvesystem 30. The ECM 42 actuates the exhaust valve system 30 bydeactivating the shut-off valve 44, which permits the flow of oil to theexhaust valve gallery 52.

Referring now to FIG. 4A-4B, when the exhaust valve actuation system 30is actuated, at least one of the cylinders C1 is deactivated using highpressure oil to force the exhaust valve 32 at least partially open. Theshut-off valve 44 is deactivated, which permits oil from the injectoroil gallery 54 to flow to the exhaust valve gallery 52, which in turn,permits oil to be distributed to a piston assembly 60 that correspondsto the cylinder C1 (or cylinders C1, C3, C5) to be deactivated. The oilin the piston assembly 60 causes a piston 62 to displace from aretracted position (FIG. 3B) to a deployed position (FIG. 4B), whichdisplaces an exhaust valve bridge 64. Displacement of the exhaust valvebridge 64 forms an opening 66 between the exhaust valve seat and anexhaust valve 32 of the engine cylinder C1.

With the exhaust valve 32 opened, the heated compressed air flows out ofthe opening 66, to the exhaust manifold 38 and is fluidly communicatedto the DPF 24. At the exhaust manifold 38, the heated compressed airfrom the deactivated cylinders C1, C3, C5 is combined with the heatedexhaust gas from the activated cylinders C2, C4, C6, and gases from bothsources are fluidly communicated to the DPF 24.

Simultaneously or in quick succession with opening of the exhaust valve32, the ECM 42 de-activates the injectors 40 of the de-activatedcylinders to prevent fuel injection in the de-activated cylinders C1,C3, C5. However, the injectors 40 in the activated cylinders C2, C4, C6remain activated.

It is possible that in the deactivated cylinders C1, C3, C5, even thoughthere is no combustion at these cylinders during exhaust valve systemactuation, that the fuel injectors 40 can inject fuel to be fluidlycommunicated downstream through the exhaust manifold 38 and to the DPF24. The fuel may be combusted at the DOC 26 or upstream of the DOC,resulting in additional heat at the DPF for regeneration.

After regeneration occurs, as indicated by the exhaust back pressuresensor 56 to the ECM 42 that the back pressure is below thepredetermined value, the ECM turns off the exhaust valve actuationsystem 30. When the exhaust valve actuation system 30 is turned off, apressure relief valve 68 (FIG. 2) is opened and the shut-off valve 44 isactivated, preventing the oil from the injector oil gallery 54 fromentering the exhaust valve gallery 52. Oil in the exhaust valve gallery52 drains to a sump (not shown), and the exhaust valve 32 is retractedto the retracted position (FIG. 3B) under force of at least one spring70. Normal fuel injection resumes in the formerly deactivated cylinderC1, which again becomes an activated cylinder for combustion.

The aftertreatment system 10 allows the regeneration of the DPF 24without significantly increasing the engine speed or loading. With theaftertreatment system 10, the vehicle can run on a “stop and drive”basis, where the engine 14 can be run at a lower speed and lowerloading, while at the same time, providing exhaust gas flow F with asufficiently high temperature to initiate the regeneration at the DPF24.

1) An exhaust valve actuation system of an engine having a plurality ofcylinders for initiating a regeneration event at a diesel particulatefilter of an exhaust aftertreatment system, the exhaust valve actuationsystem comprising: an engine control module associated with the engine;a plurality of exhaust valves corresponding to the plurality of enginecylinders; wherein when at least one of a predetermined amount of backpressure and a predetermined temperature is communicated to the enginecontrol module, the engine control module actuates at least one of theplurality of exhaust valves to open to permit the compression of gas orgas-fuel mixture inside the corresponding cylinder, and wherein at leastone of the plurality of exhaust valves is not actuated to open to permitcombustion inside the corresponding cylinder. 2) The exhaust valveactuation system of claim 1 wherein the exhaust valves are opened usinghigh pressure oil from a high pressure oil manifold associated with theengine. 3) The exhaust valve actuation system of claim 2 wherein thehigh pressure oil manifold has an injection oil gallery and an exhaustvalve gallery. 4) The exhaust valve actuation system of claim 3 furthercomprising a shut-off valve operable to selectively prevent and allowthe fluid communication of oil from the injection oil gallery to theexhaust valve gallery. 5) The exhaust valve actuation system of claim 4wherein when oil is communicated to the exhaust valve gallery, a pistonis displaced from a retracted position to an extended position. 6) Theexhaust valve actuation system of claim 5 wherein displacement of thepiston to the extended position opens the exhaust valve. 7) The exhaustvalve actuation system of claim 1 wherein the cylinder corresponding tothe at least one open exhaust valve compresses gas or gas-fuel mixtureresulting in heated, compressed gas or gas-fuel mixture, and the heated,compressed gas or gas-fuel mixture is fluidly communicated out of theexhaust valve to the diesel particulate filter. 8) The exhaust valveactuation system of claim 1 wherein the cylinder corresponding to the atleast one of the plurality of exhaust valves that is not open receivesan increased amount of fuel resulting in heated exhaust gas, and theheated exhaust gas is fluidly communicated out of the exhaust valve tothe diesel particulate filter. 9) The exhaust valve actuation system ofclaim 1 wherein when the engine control module does not open the atleast one exhaust valve, the corresponding cylinder is used forcombustion. 10) The exhaust valve actuation system of claim 1 furthercomprising at least one of a temperature sensor for sensing thetemperature at the aftertreatment system and a back pressure sensor forsensing the pressure at the aftertreatment system, wherein at least oneof the temperature sensor and the back pressure sensor communicate atleast one of the temperature and the back pressure to the engine controlmodule. 11) A method of regenerating an exhaust aftertreatment system ofan engine having a diesel particulate filter, the method comprising:providing a fluid passageway from the engine to the diesel particulatefilter; sensing and communicating at least one of a back pressure of theaftertreatment system and a temperature of the aftertreatment system toan engine control module, and comparing at least one of the backpressure and the temperature to a predetermined back pressure and apredetermined temperature, wherein on the basis of the comparison, theengine control module actuates at least one exhaust valve of a cylinder;opening the at least one exhaust valve to compress gas or gas-fuelmixture inside of the cylinder in response to the command of the enginecontrol module, wherein not all exhaust valves are opened by the enginecontrol module so that combustion can continue to occur at the remainingcylinders; fluidly communicating the compressed, heated gas or gas-fuelmixture from the cylinder corresponding to the opened exhaust valve tothe diesel particulate filter to initiate regeneration; and fluidlycommunicating the combusted exhaust gases from the remaining cylindersto the diesel particulate filter to initiate regeneration. 12) Themethod of claim 11 further comprising the step of the engine controlmodule deactivating a shut-off valve and permitting oil from an injectoroil gallery to flow to the exhaust valve gallery. 13) The method ofclaim 12 further comprising the step of permitting oil to be distributedto a piston assembly that corresponds to the cylinder having the exhaustvalve to be opened. 14) The method of claim 13 further comprising thestep of displacing a piston of the piston assembly from a retractedposition to a deployed position under oil pressure. 15) The method ofclaim 11 further comprising the step of injecting an increased amount offuel into the remaining cylinders for combustion. 16) The method ofclaim 11 further comprising the step of opening the exhaust valve onthree cylinders, and not opening the exhaust valve on three cylinders.17) The method of claim 11 further comprising the step of injecting fuelinto the cylinder corresponding to opened exhaust valve, and fluidlycommunicating the injected fuel to the aftertreatment system. 18) Anexhaust valve actuation system of an engine having a plurality ofcylinders for initiating a regeneration event at a diesel particulatefilter of an exhaust aftertreatment system, the exhaust valve actuationsystem comprising: an engine control module associated with the engine;at least one of a temperature sensor for sensing the temperature at theaftertreatment system and a back pressure sensor for sensing thepressure at the aftertreatment system, wherein at least one of thetemperature sensor and the back pressure sensor communicate at least oneof the temperature and the back pressure to the engine control module; aplurality of exhaust valves corresponding to the plurality of cylindersin the engine; a high pressure oil manifold associated with the engineand having a shut-off valve selectively preventing oil from an injectoroil gallery from flowing to an exhaust valve gallery; wherein when atleast one of a predetermined amount of back pressure and a predeterminedtemperature is communicated to the engine control module, the enginecontrol module deactivates the shut-off valve, permitting oil from theinjector oil gallery to flow to the exhaust valve gallery to open atleast one exhaust valve, wherein at least one of the plurality ofexhaust valves is not actuated to open by the engine control module topermit combustion inside the corresponding cylinder. 19) The exhaustvalve actuation system of claim 18 wherein the oil in the exhaust valvegallery displaces a piston from a retracted position to an extendedposition. 20) The exhaust valve actuation system of claim 19 wherein thedisplacement of the piston to the extended position opens the exhaustvalve.